The invention relates to a display instrument, in particular in a motor vehicle, which display instrument has a light-guiding pointer which is connected fixed in terms of rotation to a pointer shaft embodied as a light guide, and a LED which is secured behind the end face of the pointer shaft facing away from the pointer in order to inject light into the pointer shaft, and thus also into the pointer from a printed circuit board arranged behind a pointer drive.
Display instruments of the abovementioned type are known, In them the LED is arranged on the side of the printed circuit board facing the pointer shaft, opposite the lower end face of the pointer shaft. For this reason, the light which is emitted by the LED only needs to be injected once into the pointer shaft and deflected once in order to make it pass into the radially orientated pointer. However, in practise the arrangement of an LED on the side of the printed circuit board facing the pointer drive often causes problems because the spatial conditions are very restricted in this region. The problem is aggravated by the fact that LEDs with strong illumination which are necessary to light a pointer brightly have a particularly large overall volume.
The invention is based on the problem of configuring a display instrument of the type mentioned at the beginning which is intended for a motor vehicle in such a way that the space required for the arrangement of the LED is as small as possible.
This problem is achieved according to the invention in that the printed circuit board has an opening opposite the end face of the pointer shaft, and the LED projects into this opening.
As a result of this configuration, the cross section of the printed circuit board can be at least partially used to receive the LED, with the result that the LED does not need to project as far, or does not need to project at all, into the pointer drive, and takes up less space there. In order to simplify the orientation of the LED, it is favorable if the opening is arranged flush with the end face of the printed circuit board.
The fabrication of the display instrument is particularly cost effective if the LED is electrically connected to the printed circuit board on the side of said printed circuit board facing away from the pointer drive and projects with a lens into the opening the electrical connection of such a LED can be made by customary soldering.
The space required for the LED is particularly small if the LED is electrically connected to the printed circuit board on the side of the printed circuit board facing the pointer drive and projects with its base into the opening.
The light can be injected into the pointer shaft in a particularly low-loss fashion if, in accordance with a further advantageous development of the invention, the LED is arranged on the side of the printed circuit board facing away from the pointer drive and a lens of the LED which is embodied as a separate component, receives the light from the LED and injects it into the pointer shaft is inserted into the opening.
The lens can be secured particularly tightly to the printed circuit board and mounted very quickly by pressing or clipping on if it has a circumferential securing edge which can be pressed or clipped onto the printed circuit board.
The pointer may be illuminated with a color different from that of the LED if the lens has a coloring. Alternatively, it would be possible to conceive of using a comparatively expensive multi-color LED for changing illumination colors.
If the LED is arranged on the side of the printed circuit board facing away from the pointer drive and projects into the opening, it is then possible, in order to avoid light losses, to keep the distance between the injection face of the pointer shaft and the LED very small by virtue of the fact that the pointer shaft engages partially in the opening in the printed circuit board.
A development of the invention which is advantageous in particular in LEDs with strong illumination provides for the LED to have an element which conducts away heat. This element which conducts away heat is, in a particularly simple form, a housing of the LED which, for example, is made particularly large for this purpose. However, special elements for conducting away heat, such as cooling ribs, may also be provided.
According to another advantageous development of the invention, a reflector is arranged so as to engage in the opening in the printed circuit board, which reflector increases the usable proportion of the light of the LED which can be injected into the pointer shaft. In a particularly simple way it is possible for this reflector to be plugged or pressed into the printed circuit board or clipped to the printed circuit board.
The number of components of such a display instrument according to the invention can be advantageously reduced if, in accordance with another refinement of the invention, the reflector has an electrical conducting element for making contact with the LED.